Paper is made by a continuous process on a papermaking machine. Paper is formed at the wet end of the papermaking machine, typically by depositing a slurry of paper fibers and water on a screen to form a mat. The mat of fibers on the screen is dewatered by press rolls and suction boxes and thereafter transferred to a progression of rollers where it is pressed and dried.
The final forming step in the papermaking process is to run the web of formed paper through a calendar or super calendar which compresses the web between opposing rollers and improves the surface finish and uniformity of the paper thickness. All processes involved in papermaking, from the forming of the paper at the wet end of the papermaking machine to the calendaring at the dry end of the papermaking machine are continuous in nature and each length of the paper web is intended to be subjected to the same processes and forces, thus forming a paper web of high uniformity.
However, the final step in the papermaking process, that of winding or reeling the paper web onto spools for removal from the papermaking machine can result in non5 uniform treatment of the paper web.
Specifically, a reel of paper produced by a papermaking machine typically has a diameter of 120 inches or more and a reel width of 200 to 400 inches. The reel of paper is further processed by rewinding and slicing and sometimes coating the paper to form individual reels or sets to be used by paper consuming customers (for example, newspapers). It is known that a paper web formed on large machine reels can be damaged near the edge of the sheet or web. The damage typically results in the web breaking when it is further processed in a paper coating or rewinding machine or as it is utilized in a printing press.
A set is a smaller reel or roll of paper which has been formed on a larger, or jumbo reel. The last set is paper which is nearest the center of the reel, or the paper that is first wound on the reel spool. Studies have shown that a high percentage of rejects constitute the last set of a reel. Specifically, as set forth in U.S. Pat. No. 5,560,566, 73% of the press room paper web breaks during printing were caused by the last set off the reel, or the paper that is disposed closest to the spool when the paper of the web is wound onto the reel.
With the increase in size of the rolls of paper being produced, the problems associated with existing paper reels have been exacerbated while at the same time the tolerance of such defects or waste has decreased due to competitive pressures, concern for efficiency and utilization of natural resources.
Prior to the mid-1990s, reels for reeling paper manufactured by papermaking machines were of the so-called Pope-type reels wherein a new reel spool is initially engaged by a pair of arms while the first few wraps of paper are wound onto the reel spool. The newly started wound web is then brought into nipping engagement with a support drum while the on-coming paper web continues to be wrapped around the new roll. As the wound paper roll begins to increase in diameter, it is rotated by the primary arms about the periphery of the support drum and transferred onto substantially, horizontally disposed support rails. On almost all existing Pope-type reels, torque could not be applied to the reel spool while it was held in the primary arms. As the reeled spool is rotated down to be supported on the support rails, a pair of secondary arms then maintains the wound paper roll and nipping engagement with the support drum with the nip in a substantially horizontal plane to the rotational axis of the paper roll being wound. Torque is applied to the wound paper roll being wound generally after it has been transferred to the secondary arm.
In Pope-type reels, the wound paper roll follows a complicated, non-smooth path from a location where the on-coming web is initially wrapped onto the new reel spool, to a point where it is brought into nipping engagement with the support drum and then rotated downwardly about the periphery of the support drum by the primary arms to the point where it is supported by the support rails as it is moved horizontally on the rails as the diameter of the wound web increases.
As set forth in U.S. Pat. Nos. 5,370,327, 5,554,841, 5,560,566 and 5,673,870, all assigned to Beloit Corporation, a substantial improvement to the Pope-type reel has been provided in the form of the TNT (torque, nip and web tension) type of reel disclosed in said patents. The solution provided by the TNT reels is to produce a more uniformly wrapped paper web on the reel by providing a support drum that moves translationally downwardly while maintaining nipping contact with the newly started reel spool as the reel spool passes over the support drum apex to the downstream side of the support drum while the reel spool maintains continuous supporting contact on the rails. In the embodiment disclosed in U.S. Pat. No. 5,370,327, actuators are provided on the downstream side of the support drum which enable the support drum to maintain continuous contact with the web roll until it reaches its desired diameter. A similar apparatus with respect to the support drum is disclosed in U.S. Pat. No. 5,544,841.
In contrast, in U.S. Pat. Nos. 5,560,566 and 5,673,870, the support drum is maintained in a stationary position and the nip pressure or nip load between the support drum and the roll is controlled by the force of gravity, the position of the roll along the rails and a conventional pneumatic or hydraulic cylinder or screw mechanism. In short, instead of adjusting the position of the support drum to adjust nip pressure, the nip pressure is controlled by manipulating the roll or reel.
In the designs disclosed in all of the aforementioned patents, the support drum is maintained in a level position. However, it has been found that certain instances may occur where it may be desirable to adjust the position of the support drum so that it deviates from a level or horizontal position in order to maintain a uniform nip load across the roll. Further, it has also been found that once the roll has passed over the support drum, it may be desirable, and necessary, to reduce the degree to which the support drum deviates from a horizontal or level position to ensure proper winding. A deviation in the position of the support drum from a level or horizontal position is often referred to as backlash. In short, it has been found that it would be desirable to be able to adjust the backlash settings, or the vertical position of one end of the support drum with respect to the other, during machine operation. Currently, no such apparatuses exist which would permit such a backlash adjustment during the operation of a papermaking machine.